Biomagnetic susceptometry is the most effective method for monitoring iron stores in body organs. Unfortunately, the existing instruments, based on Superconducting Quantum Interference Devices, are too expensive for wide use. A less expensive biomagnetic suspectometer is badly needed. We propose to develop such an instrument, using room- temperature sensors instead of SQUIDS. Our analysis indicates that, where the SQUID systems rely on properties unique to superconductors, we can achieve comparable results with carefully designed measurement techniques. Key elements of our system include (1) new magnetic sensors with reduced noise, (2) an excitation coil design that cancels the applied magnetic field at the sensor locations, and (3) techniques to minimize fluctuations in the geometry of the coil system. The room- temperature biosusceptometer will be simple, reliable, and inexpensive it will be available sooner than any SQUID system; and it will make body iron measurements available to a much wider range of patients. In Phase I, we will establish technical feasibility by demonstrating that a room-temperature instrument can measure the weak magnetic response of liver iron, in the presence of other body tissues. During Phase II, we will develop an optimized instrument and demonstrate its effectiveness in clinical experiments.